Old germ is now more dangerous

A new, more dangerous strain of a germ that has long caused diarrhea in hospital patients is now widespread in the United States, causing severe, sometimes deadly outbreaks around the country, researchers reported Thursday.

Strains of the germ have been detected among people who have never been in the hospital, raising alarm that the infection may be emerging more widely and posing a broader public health threat, the researchers said.

While the infection does not pose a public health emergency, doctors and patients need to be aware of the risk so cases can be identified and treated quickly and measures can be taken to limit its spread, experts said. They do not yet have good estimates of how many people have been infected.

The germ may have emerged in part due to the overuse of antibiotics, the experts added, and its emergence provides another reason to use antibiotics as judiciously as possible.

“We are very concerned about this,” said L. Clifford McDonald of the federal Centers for Disease Control and Prevention. “It’s still probably an unusual occurrence in healthy people, but we’re concerned enough that we want to alert people.”

The bacterium, known as Clostridium difficile, has long been known to cause diarrhea in hospitals, particularly in patients who are taking antibiotics for other reasons. The antibiotics kill other microbes that keep C. difficile in check, allowing it to grow and cause illness. Such infections, however, had usually been easily treatable with other antibiotics.

In recent years, though, unusually severe outbreaks of the infections have been reported around the world. In 2003, a particularly severe outbreak among hospital patients in Quebec killed perhaps more than 200 people.

In three new reports released Thursday by the CDC and the New England Journal of Medicine, researchers identified the strain responsible for the Quebec cases, determined that the same strain is present throughout the United States, and described other cases outside of hospitals.

Taken together, the research indicates that the bacteria poses a widening health problem, researchers said.

“There is a new strain of Clostridium difficile that is causing epidemics in many hospitals in the United States,” said John Bartlett of Johns Hopkins University School of Medicine in Baltimore, who co-authored an editorial in the journal. It was released early along with two research papers because of their public health importance. “It’s a bad bug,” Bartlett said.

In one of the reports released Thursday, Vivian Loo of McGill University reported that the strain of bacteria responsible for the Quebec outbreak had mutated to be more resistant to a widely used class of antibiotics known as fluoroquinolones. The infection killed 6.9 percent of infected patients, a far higher mortality rate than usually associated with the infection.